Devices are well known in the art which control exhaust emissions by the oxidization of HC and CO and reduction of NO.sub.x components present in exhaust gas emitted from an internal combustion engine by use of a catalyst. However emission control performance is relatively low when a catalyst is not sufficiently activated as, for example, in a low temperature gas environment produced immediately after cold-starting an engine.
Attempts have been made to absorb HC components from low temperature exhaust gas emissions by using an HC absorbent material which absorbs HC from the exhaust gases thus preventing such components from being emitted into the atmosphere. However such HC absorbent materials release bound HC when the temperature exceeds a certain level and thus can only be used in a low temperature exhaust gas environment. Furthermore the temperature at which HC release is initiated is generally lower than the activation temperature of the catalyst and so when the temperature of the exhaust gas exceeds the temperature at which HC release is initiated but is lower than the activation temperature of the catalyst, HC is released into the atmosphere.
Tokkai-Hei-8-224449 discloses a catalyst converter which comprises a lower layer comprised an HC absorbent material and an upper layer formed from a catalyst which are formed on a honeycomb-shaped catalyst carrier. In this way, HC permeating the catalyst layer at low temperatures is absorbed by the HC absorbent material on the lower layer. When such bound HC is released from the HC absorbent material due to rises in temperature, the HC is oxidized by the action of the catalyst when passing through the upper catalyst layer.
However even in this case, the HC absorbent material releases bound HC at temperatures lower than the catalyst activation temperature for example at 150-200.degree. C. As a result, if the catalyst is not activated, released HC is not oxidized and unavoidably released directly into the atmosphere.